Add success-client-cache status for image scaler

See merge request gitlab-org/gitlab-workhorse!656

Since we weren't counting cached responses as successes, in Prometheus there were showing up as `unknown`, which contributes to the overall error budget.

We need to follow up with a runbook change that also counts cached responses as successes.

[ci skip]

Implement conditional GETs for image resizer

See merge request gitlab-org/gitlab-workhorse!647

We now set a `Last-Modified` header based on either local
file timestamps or the respective header returned from an
object storage provider.

Use detected file format for image scaler

See merge request gitlab-org/gitlab-workhorse!651

Make decisions based on what Go's `image.DecodeConfig`
tells us the image format actually is
instead of using the data sent from Rails app.

Rework image scaler tests

See merge request gitlab-org/gitlab-workhorse!650

We all test this in the module now

jaeger: limit operation cardinality by using route regex

See merge request gitlab-org/gitlab-workhorse!648

Update release steps - NO CHANGELOG

See merge request gitlab-org/gitlab-workhorse!645

Now mentions that the gitlab repo also needs to be updated
for the version to be deployed to .com.

Document  workhorse mission and how to add new features - NO CHANGELOG

See merge request gitlab-org/gitlab-workhorse!637

Our markdown processor do not allow embedding videos.

Update raven-go and gocertifi packages

See merge request gitlab-org/gitlab-workhorse!644

Adjust image scaler latency buckets

See merge request gitlab-org/gitlab-workhorse!643

These looked misaligned. According to production logs, we currently serve 99% of all those requests in less than 200ms.

The updated gocertifi package has a properly-recognized LICENSE file for
the license_finder gem.

raven-go has minor changes:
https://github.com/getsentry/raven-go/compare/v0.1.0..v0.2.0

[ci skip]

Remove unnecessary config struct pointers NO CHANGELOG

See merge request gitlab-org/gitlab-workhorse!642

Add a metric that tracks max image scaler processes

See merge request gitlab-org/gitlab-workhorse!640

Exclude dot-files from being linted

See merge request gitlab-org/gitlab-workhorse!641

This was matching `.go` files in my local `.git` folder.

Let's just exclude all hidden files.

This will allow us to compute a saturation metric to see
how close we are to exhausting this `actual / max`.

Refs https://gitlab.com/gitlab-com/runbooks/-/issues/52

Add a total-requests metric for the image scaler

See merge request gitlab-org/gitlab-workhorse!638

Broken down by a `status` label

Clean up main.go NO CHANGELOG

See merge request gitlab-org/gitlab-workhorse!639

Set default max image scaler procs to num_cpu / 2

See merge request gitlab-org/gitlab-workhorse!635

This is a more realistic value for a single node setup and development.

The recommendation is to use num_cores / 2 as a guideline.

Simplify config handling in main()

See merge request gitlab-org/gitlab-workhorse!634

Don't log "success" when failing over to original image

Closes #311

See merge request gitlab-org/gitlab-workhorse!636

Add route for Debian package uploads

See merge request gitlab-org/gitlab-workhorse!610

See https://gitlab.com/gitlab-org/gitlab/-/merge_requests/42670